In welding technology a diversity of welding processes are present. These processes include for example tungsten inert gas welding (TIG), MIG/MAG and submerged arc welding (SAW). In TIG technology an arc is generated between a non-consumable electrode and the work piece. If desired a metal filler is fed into the arc. The TIG technology is suitable for welding in thin materials, in particular welding of thin aluminum work pieces. In MIG/MAG and submerged arc welding, an arc is generated between a consumable electrode and a work piece. MIG/MAG is suitable for welding of all kinds of metals at medium thickness. In TIG and MIG/MAG welding a weld puddle generated by the arc is protected by a gas supplied from a shield cup arranged at a welding torch. In submerged arc welding (SAW) an arc is generated between a consumable electrode and a work piece under a protective layer of flux covering the work piece at the arc. MIG/MAG is suitable for welding of all kinds of metals where high deposition rates are required, such as when welding in thick materials.
In the field of welding different parameters may be adjusted to achieve a desired result. These parameters includes welding voltage, welding current, electrode feed speed and welding propagation speed.
Furthermore, welding processes may be performed by a direct current process with an output from the power source connecting the electrode to the negative potential, a direct current process with an output from the power source connecting the electrode to the positive potential or as an alternating current process where the electrode switches between electrode negative and electrode positive. Generally electrode negative provides for a wide weld bead with low penetration and electrode positive provides for a narrow bead with deep penetration. The alternating current process can be seen as a process having properties in between the DC-negative and DC-positive process. Generally the alternating current has a base frequency of around the net frequency. Optionally, the frequency can be higher, that is the region of 200-400 Hz. High frequencies will generate losses in welding cables and is therefore not suitable for many applications.
Welding power sources that may operate in either DC mode or AC mode are previously known. One example is disclosed in U.S. Pat. No. 4,517,439 where separate AC and DC terminals are provided.
Even though the prior art is rich when it concerns improvements in control of the welding power supplies to generate weld seams with high quality, it is desirable to provide further improved methods for operating welding power supplies.
It is thus an object of the present invention to provide an improved method of operating a welding power supply during a welding process.